421 



LEUCITE. 



LIBETHENITE. 



422 



was necessary. Of this pigment, that obtained from the scales of 

 roach and dace was the least valuable ; that from the bleak was in 

 much greater request ; but the white-bait afforded the most delicate 

 and beautiful silver, and obtained the highest price, partly from the 

 prohibitory regulations affecting the capture of this little fish, the 

 difficulty of transmission, and rapid decomposition." (Yarrell, 

 'History of British Fishes.') 



LEUCITE (A mphigene), a Mineral which occurs imbedded in lava, 

 in trapezoidal crystals and massive. The primary form is a cube. 

 The cleavage is parallel to the planes of the cube and the rhombic 

 dodecahedron. Fracture conchoidal, undulating, shining. Hardness 

 5-5 to 6. Scratches glass with difficulty. Colour yellowish, grayish, 

 or reddish-white. Streak white. Lustre vitreous. Transparent, 

 translucent, opaque. Specific gravity 2'483. 



^ Massive variety amorphous, granular. Reduced to powder, it 

 renders vegetable blues green. Before the blow-pipe alone it is 

 infusible ; with borax difficultly forms a clear glass. 



Analysis by Klaproth, from Vesuvius (No. 1), and by Arfvredson, 

 from Albauo (No. 2) : 



No. 1. No. 2. 



Silica 53-75 56-10 



Alumina 24-62 23-10 



Potash 21-35 21-15 



Oxide of Iron .... 0-95 



99-72 101-30 



LEUCO'JUM, a genus of Plants belonging to the natural order 

 Amaryllidactce. It has a 6-parted perianth, bell-shaped ; the segments 

 all equal, and thickened at their points ; the stamens equal. 



L. cettivum, the Summer Snow-Flake, has a many-flowered spathe ; 

 a style thickened upwards. The height is from 2 to 2$ feet. The 

 flowers are white and drooping ; the tips greenish. Leaves broadly 

 linear, keeled ; scape 2-edged; spathe usually as long as the flowers. 

 It is found in wet meadows in Great Britain. 



LEUCOPHANE, a Mineral occurring crystallised in four-sided 

 prisms, but is seldom regularly crystallised. Cleavage imperfect in 

 three directions. Colour pale dirty-green and deep wine-yellow. 

 Transparent and colourless in thin fragments. Lustre vitreous on 

 cleavage surface. Hardness 3'50 to 3'75. Specific gravity 2'974. It 

 is found at Langesundfiord in Norway. Its analysis by Erdmann 

 i;iv.-s - 



Silica ... .... 47-82 



Glucina 11-51 



Lime 25-00 



Fluorine 6-17 



Sodium 7-59 



Protoxide of Manganese 1-01 



Potassium 0-26 



99-36 



LEUCOSIA. [OXTSTOMA.] 



LEVYNE,'a Mineral occurring crystallised. Primary form an acute 

 rhomboid. Cleavage parallel to its planes. Fracture conchoidal. 

 Hardness 4'0. It scratches carbonate of lime. Colour and streak 

 white. Lustre vitreous. Translucent. Specific gravity 2'15. When 

 heated it yields water, and becomes opaque ; swells up when heated 

 on charcoal ; with phosphoric salt gives a transparent globule, which 

 contains a nucleus of silica, and becomes opaque on cooling. It is 

 suspected to be merely a variety of Chabasile. It is found in Ireland, 

 Faroe, and some other places. Analysis by Berzelius : 



Silica 48-00 



Alumina 20'00 



Lime 8'35 



Soda 2-75 



Potash 0-41 



Magnesia 0-40 



Water 19-30 



99-21 



LEYCESTE'RIA, a genus of Plants belonging to the natural order 

 Kubiacere, named after the late W. Leycester, Esq., of the Bengal 

 Civil Service, who paid much attention to horticulture in India. The 

 genus consists of only a single species. 



L.formota is a native of the Himalaya Mountains, at elevations of from 

 6000 to 7000 and 8000 feet, in Nepaul and Sirmore, where it grows 

 among oaks and pines, and is therefore well suited to the climate of 

 England, where indeed it may be seen growing in great luxuriance in 

 some gardens, and showing that many others from the same situations 

 are equally suitable to this climate, which is not the case with many 

 shrubby Rubiaceous plants. It forms a large and very showy shrub, 

 with numerous luxuriant smooth and cylindric fistulous shoots issuing 

 from the root, which are of a purplish colour. The leaves are opposite, 

 ovate-lanceolate, and glaucous; the flowers white, with a tinge of 

 purple, arranged in drooping racemes, which are furnished with 

 coloured foliaceous bracts. 



LI'ALIS, a genus of Reptiles. 



LIAS, in Geology, the name of a series of argillaceous nnd 



calcareous strata, forming the basis of the Oolitic System. The term 

 was originally applied, in the south of England, to the calcareous 

 beds which are at the bottom of the thick argillaceous deposits, now 

 ranked in the Lias Formation. The lime burnt from the lias of 

 Aberthaw, Bath, and Barrow-on-Soar, has the valuable property of 

 setting in water. [OOLITIC SYSTEM.] 



LIBELLULA. [LIBELLULIDJE.] 



LIBELLULID^E, a family of Neuropterous Insects, of which the 

 Common Dragon-Fly is the type. The Dragon- Flies have horny strong 

 mandibles and maxillae, covered by the labrum and labium ; their tarsi 

 are 3-pointed ; then- wings are equal ; the posterior extremity of the 

 abdomen is furnished with hooks or peculiar appendages. The size, 

 beauty, and habits of these insects have rendered them favourite 

 objects of study with the entomologist. In the larva state they live 

 entirely in the water, engaged in unceasing war with other insects, 

 which by singular devices they entrap and devour. Their pupa state 

 is also passed in water, and, contrary to the usual habit of insects, 

 is a period of activity and locomotion. They are then furnished with 

 an extraordinary mask, formed out of that part of the head which 

 replaces the lower lip, and by which they cover the jaws and the 

 whole under part of the head. They use it to alarm and seize their 

 prey, projecting it at will. When perfect insects they become inhabit- 

 ants of air, and are endowed with extraordinary power of flight and 

 precision of movement, performing astonishing evolutions. Their 

 habits continue as ferocious as they were before. When taken and 

 imprisoned they have been known to devour their own bodies ! 

 Several valuable monographs have been published on these interesting 

 insects by De Geer, Roesel, Vander Linden, and Charpentier ; but the 

 most important is that of M. de Selys Longchamps, entitled ' Mono- 

 graphic des Libellulide'es d'Europe." In this work 61 species are 

 described, arranged under the genera Libellula, Cordulia, Lindenia, 

 Gomphus, Cordulegaster, jEshna, Anax, Caleptery.e, Leste, Sympecma, 

 and Agrion. 



In the arrangement of Westwood (' Introduction to the Modern 

 Classification of Insects') the genera of Libetlididie inhabiting Great 

 Britain are grouped under two sub-families, Libellulldes and Agrio- 

 nida. The following table exhibits the chief characters of the 

 British genera : 



Sub-Family 1. LibeUulidea. 



Anax (1 species) ; anal angle of 



posterior pair of wings rounded. 



jfjfhna (7 species) ; anal angle of 



A. Ocelli in a row posterior pair of wings more or 



less angulated in the male. 

 Cordulegaiter (\ species) ; anal 

 angle of posterior wings strongly 

 angulated. 



B. Ocelli in a line; eyes remote . Gomphus (2 species). 



( Cordulia (3 species) ; anal angle 

 of posterior wings angulated in 

 x> /i it A i the male. 



C. Ocelli in a triangle . . . UfWZWa (15 species) ; anal angle 



of posterior wings rounded in 

 both sexes. 



Sub-Family Z.Agrionidet. 



(Agrion (13 species) ; stigma rhom- 

 boidal ; areolets mostly quad- 

 rangular. 



Lestes (3 species) ; stigma oblongo- 

 quadrate ; areolets mostly pen- 

 tagonal 



B. Wings coriaceo-membranous ; 1 , 

 stigma obsolete / Calepteiyx (4 species). 



LI'BER, the inner bark of a plant, is a layer consisting of woody 

 tissue, cellular substance, and vessels of the latex, forming a compact 

 zone immediately applied to the wood. The woody tissue of which it 

 is composed quickly becomes . thick-sided, by the addition of internal 

 ligneous strata, the consequence of which is that such tissue in this 

 part is more tough than elsewhere. Hence it is usually from the 

 liber that are extracted the fibres employed in making cordage or 

 linen-thread : this at least is its source in hemp, flax, the lime-tree, 

 the lace-bark, and the many other Exogens which furnish thread ; 

 but in Endogens, which have no liber, as the Cocoa-Nut, it is the 

 ordinary woody bundles of the leaves, stem, and husks of the fruit 

 from which the fibre used for ropes is procured. It is said that 

 certain Exogens, such as Menispermacece, have no liber. (' Comptes 

 Rendus,' v. 393.) In many plants a new layer of liber is formed 

 annually, comtemporaneously with a new layer of wood, but this is 

 by no means universal ; on the contrary, the oak and the elm increase 

 their liber slowly and irregularly. [BARK.] 



LIBETHENITE, Phosphate of Copper, a Mineral occurring in small 

 octohedral crystals and in radiated masses. Primary form a right 

 rhombic prism. Colour dark green. Streak green. Fracture uneven. 

 Hardness 4'0. Transparent, translucent. Lustre resinous. Specific 



A. Wijgs membranous 



